K12LTSP is a modification to the Centos operating system with the Linux Terminal Server Project (LTSP) packages integrated into it. It is designed to be easy to install and configure. K12LTSP is an offshoot of the Linux in School Project (K12Linux).
K-12 is often used in the United States to refer to grade school from kindergarten through high school (12th grade).
References
K12LTSP Wikipedia(Text) CC BY-SA